Agricultural systems are embedded in wider social-ecological processes that must be considered in any complete discussion of sustainable agriculture. Just as climatic profiles will influence the future viability of crops, institutions, i.e., governance agreements, rural household and community norms, local associations, markets, and agricultural ministries, to name but a few, create the conditions that foster sustainable food systems. Because discussions of agricultural sustainability often overlook the full range of social dimensions, we propose a dual focus on a broad set of criteria, i.e., human health, labor, democratic participation, resiliency, biological and cultural diversity, equity, and ethics, to assess social outcomes, and on institutions that could support diversified farming systems (DFS). A comparative analysis of case studies from California's Central Valley, Mesoamerican coffee agroforestry systems, and European Union agricultural parks finds that DFS practices are unevenly adopted within and among these systems and interdependent with institutional environments that specifically promote diversified farming practices. Influential institutions in these cases include state policies, farmers' cooperatives/associations, and organized civic efforts to influence agroenvironmental policy, share knowledge, and shape markets for more 'sustainable' products. The Californian and Mesoamerican cases considers organic and fair trade certifications, finding that although they promote several DFS practices and generate social benefits, they are inadequate as a single strategy to promote agricultural sustainability. The complex governance and multifunctional management of Europe's peri-urban agricultural parks show unexpected potential for promoting DFS. Unless DFS are anchored in supportive institutions and evaluated against an inclusive set of social and environmental criteria, short-term investments to advance diversified agriculture could miss a valuable opportunity to connect ecological benefits with social benefits in the medium and long terms.